Research is proposed in three areas: (1) Synthesis of model Co-and Fe-porphyrin systems for the study of the molecular basis for heme-heme interactions (e.g., cooperativity of oxygen uptake in hemoglobin), for assessment of the role of the globin in the thermodynamics of interaction of hemoglobin with small molecules, such as oxygen, and for assessment of the molecular basis of possible ligand-globin interactions; (2) synthesis and characterization of Cu(I)-nitrogenous base dimers as models for hemocyanin and study of the interactions of such models with molecular oxygen; (3) structural characterization of models for nonheme-iron dioxygenases.